This relates generally to graphics processing and particularly to anti-aliasing.
Geometric aliasing is a major problem in three dimensional (3D) graphics. Non-axis aligned triangle edges cause ugly staircase artifacts, and fine geometrical detail gives rise to flickering and aliasing as primitives may fall in between samples. This is fundamentally a signal processing problem as the rasterizer point samples the image signal, which has infinite frequency content due to sharp discontinuities.
Current solutions either perform post-processing to attempt to remove the aliasing artifacts, or use multiple samples per pixel to reduce aliasing (e.g., multi-sampled anti-aliasing (MSAA)). Post-processing is fundamentally limited by the initial sampling, while using multiple samples is expensive in terms of bandwidth and power as multiple samples per pixel are stored for the entire screen. Color and depth buffer compression aim to reduce the bandwidth, but the required bandwidth is still large compared to non-multisampled rendering. In regions of high complexity, compression often breaks down.
Aliasing primarily occurs at geometrical discontinuities, i.e., the silhouette edges of an object or interior silhouette edges at creases in a surface, at shading discontinuities, or due to primitives falling between sample points. However, MSAA performs anti-aliasing of all triangle edges and stores multiple samples (color and depth) for all pixels, even in the interior of triangles. This results in an unnecessarily high bandwidth and often redundant shading along shared edges. At high sampling rates, the bandwidth and memory become prohibitive. MSAA does not fully address the problem of small primitives that may still fall in between the sample points.